This invention relates to surveying instrument sensors in general, and more particularly to a surveying instrument sensor utilizing two two-axis flexure suspended gyros in a rate capture and gimbal stabilized mode for oil well pipe surveying.
In oil well pipe surveying, it is necessary to obtain accurate information concerning the path of the pipe down to depths of 20,000 to 30,000 feet. The typical manner of accomplishing such surveying has been to measure the tilt angle of the pipe at discrete depths as the sensor package is lowered into a well. Traditionally, geographic heading has been provided through the use of a miniature directional gyroscope. The drift of such a gyroscope is enchanced by calibration at each measurement level.
The primary disadvantages of such a technique are that it provides inadequate accuracy, requires excessive measurement times and exhibits a short instrument life, particularly when applied to deep wells of 20,000 to 30,000 feet depth, in which cases ambient temperatures of up to 350.degree. F. can be encountered.
Thus, the need for an improved surveying instrument sensor which is capable of quickly providing surveying data for deep wells is evident.